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<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        // 输入月份，显示当月的天数（使用case 穿透简化代码）1-12
        var month = prompt('请输入月份')
        switch(month){
            case 1:
            case 3:
            case 5:
            case 7:
            case 8:
            case 10:
            case 12:
            console.log(month+'月31天');
            break
            case 2:
            console.log(month+'月29天');
            break
            default:
            console.log(month+'月30天');
            
        }
    </script>
</body>
</html>